Skateboards generally include two trucks mounted to the bottom of the deck that allow for the skateboard to travel over various surfaces and provide the turning mechanism and restorative forces during turns. Particularly, trucks are the mechanisms that allow the deck to roll about its forward vector while all wheels remain in contact with the ground as the board and skater perform a turn. Traditional truck designs are many and varied, some of which rely on elastomer bushings while others rely on metallic compression springs to provide restorative forces which provide response to the rider and ultimately return the deck to a level position.
FIGS. 1-3 show a traditional spring-assisted skateboard truck 10 (e.g., Original S8 Carving Trucks, available at https://originalskateboards.com/product/original-s8-200 mm-carving-trucks/). Traditional trucks 10 are generally mounted to an extension riser block 12 from the bottom or top surface of the deck 14, and further may include an additional riser block 16 mounted between the truck 10 and the extension riser block 12 to provide clearance between the deck 14 and the wheels 18, 20. The riser block 16 provides clearance between the outside wheel edge and the bottom deck surface during turns such that there is no “wheel bite”. Some wedge-shaped riser blocks 16 can be used to change the angle of the center of rotation of the truck mechanism.
The traditional spring-assisted truck 10 includes a base plate 22 with opposing pivot cups 24, 26. The truck 10 receives a hanger 28 and spring 30 within the space between the pivot cups 24, 26, and a kingpin 32 (e.g., bolt) is used to secure the hanger 28 and spring 30 to the base plate 22. The hanger 28 includes an axle 34 extending therethrough for rotatably mounting of the wheels 18, 20 to the hanger 28. As shown in FIGS. 2 and 3, the truck 10 includes a plastic wave cam 36 mounted within the pivot cup 24. During tuning of the truck 10, a hex wrench 40 is used to tighten the kingpin 32 into a locknut 38. Particularly, the pivot cup 24 includes a cutout 42 (e.g., locktab slot) at one or more places along the perimeter of the pivot cup 24 configured to receive a locking key 44 (e.g., a locktab). The nut 38 is positioned over the locking key 44 such that tightening the kingpin 32 guides the locking key 44 into the cutout 42 in the pivot cup 24. As shown in FIG. 3, the locking key 44 therefore extends through the perimeter of the pivot cup 24 through the cutout 42.
As shown in FIG. 2, tuning of traditional spring-assisted trucks 10 generally involves tightening the kingpin 32, thereby preloading the compression spring 30 until the wave cam 36 extends from the end of the pivot cup 24 by a predetermined distance 46 (e.g., approximately 1 mm). The traditional kingpin 32 generally includes a threaded end that receives the nut 38. The threads on the threaded end extend approximately 20 mm in length from the endpoint of the kingpin 32, allowing the nut 38 to be threaded onto the kingpin 32 up to a maximum of 20 mm from the endpoint of the kingpin 32. The desired predetermined distance 46 is located between the endpoint of the kingpin 32 and the maximum of 20 mm from the endpoint along the threads, resulting in an approximation of how far the nut 38 should be tightened onto the kingpin 32. Because tuning of the truck 10 is performed by approximation and the extended length of the threads on the kingpin 32 allow for the nut 38 to be tightened up to the 20 mm point, overtightening of the kingpin 32 such that the wave cam 36 does not extend from the end of the pivot cup 24 can occur, resulting in catastrophic loads on the truck 10, pivot cup 24 and/or wave cam 36 during normal use of the skateboard.
This approximation is tight enough for the wave cams 36 to be axially compressively preloaded by the spring 30 in such a way that as the deck rolls about its forward vector and the hanger 28 rotates to keep the wheels 18, 20 in contact with the ground, the wave cams 36 slide in opposite-handed directions, thereby compressing the restorative compression spring 30. If there is no preload and there is total travel in the spring 30, the plastic wave cams 36 are overly constrained by the leverage of the rider. In this condition, the excessive strains exceed the wave cam 36 ultimate yield strain, resulting in cracked or shattered wave cams 36. The broken wave cam 36 fragments can fall out of the pivot cup 24 (e.g., through the distal end of the pivot cup 24) leading to a dangerously unstable mechanism and perilous circumstances for the skateboard rider. In addition, increased structural pressure can result in, e.g., fracture 48 of the pivot cup 24 at a weak point created by the locktab slot or cutout 42 (see, e.g., FIG. 4), fracture 50 of the locking key 44 at the cutout 42 (see, e.g., FIG. 5), combinations thereof, or the like. Replacement of the fractured the base plate 22 or locking key 44 leads to a significant increase in maintenance costs for the skateboard.
Thus, a need exists for a spring-assisted skateboard truck assembly that eliminates structural weak points in the base plate to prevent structural failure of the pivot cup containing the wave cam, thereby increasing safety and reliability while reducing overall maintenance costs of the skateboard. Another need exists for a compressive spring having adequate total travel and safe travel which fits within the volume defined by the baseplate. A further need exists for a kingpin that provides for a maximum tightened position so as to prevent overtightening of the spring/wave came assembly. These and other needs are addressed by the skateboard base plates and associated systems of the present disclosure.